1. Field of the Invention
The present invention relates to an optical semiconductor device having both light emission and light reception and being used for optical information processing, optical measurement, optical communications and the like.
2. Description of the Related Art
In recent years, as optical semiconductor devices used for optical information processing, optical measurement, optical communication and the like, ones have come to be used in which a light source and a light receiving portion (photodetector) are provided in the same package.
A conventional optical semiconductor device will be described. FIG. 19 is a plan view schematically showing a plane layout of the conventional optical semiconductor device. FIG. 20 is cross-sectional view schematically showing the cross section of FIG. 19 taken on the line 20-21. FIG. 21 is a cross section of FIG. 19 taken on the line 21xe2x80x9421.
In FIGS. 19, 20 and 21, a semiconductor substrate 1 is made of, for example, Si, and has a rectangular concave portion 1a on the surface thereof. A semiconductor laser element 2 is made of, for example, GaAs, and acts as a light source for emitting signal detecting light. The semiconductor laser element 2 is mounted in the concave portion 1a so that the optical axis of the signal detecting light is substantially parallel to the surface of the semiconductor substrate 1, and is integrated with the semiconductor substrate 1.
The concave portion 1a is formed so that the signal detecting light from the semiconductor laser element 2 is reflected at the inclined side surface of the concave portion 1a that is opposed to the signal detecting light emitting side of the semiconductor laser element 2 in the direction substantially perpendicular to the surface of the semiconductor substrate 1. In the part of the bottom surface of the concave portion 1a where the semiconductor laser element 2 is mounted, although not shown, one electrode for applying a voltage to the semiconductor laser element 2 is formed. The other electrode of the semiconductor laser element 2 is formed on the top surface of the semiconductor laser element 2.
Light receiving portions 3 to 8 for signal detection are, for example, impurity diffused regions, and are formed outside the concave portion 1a on the surface of the semiconductor substrate 1. For example, when the signal detecting light emitting side of the semiconductor laser element 2 on the surface of the semiconductor substrate 1 is the front side of the semiconductor laser element 2, the light receiving portions 3 to 8 are selectively formed at the left and right sides of the concave portion 1a. 
The semiconductor substrate 1 and the light receiving portions 3 to 8 are opposite in conductivity type. Between the semiconductor substrate 1 and the light receiving portions 3 to 8, a voltage that causes a reverse bias is applied.
A monitor region 12 is, for example, an impurity diffused region, is disposed in the rear of the concave portion 1a on the surface of the semiconductor substrate 1, and detects the quantity of the signal detecting light from the semiconductor laser element 2. The semiconductor substrate 1 and the monitor region 12 are opposite in conductivity type. Between the semiconductor substrate 1 and the monitor region 12, a voltage that causes a reverse bias is applied. The impurity concentration of the monitor region 12 is approximately the same as that of the light receiving portions 3 to 8.
In this optical semiconductor device, as shown by the arrow 9 in FIG. 21, the signal detecting light from the semiconductor laser element 2 is emitted in a direction substantially parallel to the surface of the semiconductor substrate 1, and is reflected at the inclined side surface of the concave portion 1a situated in front to exit in a direction substantially perpendicular to the surface of the semiconductor substrate 1.
The light receiving portions 3 to 8 are formed in positions outside the emission direction of the signal detecting light from the semiconductor laser element 2 in order that the carriers generated by the incidence of the signal detecting light from the semiconductor laser element 2 on the semiconductor substrate 1 do not adversely affect the signal detection levels of the light receiving portions 3 to 8. For example, when the signal detecting light emitting side of the semiconductor laser element 2 is the front side of the semiconductor laser element 2, the light receiving portions 3 to 8 are formed at the left and right sides of the semiconductor laser element 2 and at the left and right sides of the concave portion 1a on the surface of the semiconductor substrate 1. The light receiving portions 3 to 8 may be formed in any positions that is in a periphery of the semiconductor laser element 2, particularly outside the concave portion 1a. The number of light receiving portions is at least one.
The operation of the optical semiconductor device structured as described above will be described. First, the signal detecting light emitted from the semiconductor laser element 2 passes through an objective lens (not shown) and is condensed onto an optical recording medium (not shown). Consequently, the light corresponding to the signals of the optical recording medium is reflected and condensed onto the light receiving portions 3 to 8, so that optical signals are output from the light receiving portions 3 to 8. In this case, the quantity of the signal detecting light from the semiconductor laser element 2 is monitored by the monitor region 12, and the semiconductor laser element 2 is controlled so that the quantity is constant.
In the structure of the above-described conventional example, the signal detecting light is emitted from the semiconductor laser element 2 in the direction shown by the arrow 9, and unnecessary light (hereinafter, referred to as stray light) is generated in addition to the signal detecting light.
The stray light will be concretely described. The light associated with the optical semiconductor device includes the laser light emitted from the semiconductor laser element 2 (the light emitted from the front surface and the light emitted from the rear surface) and the return light by the reflection at a medium such as an optical disk or a magneto-optic disk. The light regarded as a problem in the present invention is the stray light due to the laser light emitted from the semiconductor laser element 2.
Laser light includes light effective in signal detection and light ineffective in signal detection. Laser light is emitted so as to spread 180 degrees both in the vertical and the horizontal directions (the larger the angle is, the smaller the light quantity is). The light emitted frontward from the front surface of the semiconductor laser element 2 is the light effective in signal detection (signal detecting light). Light emitted in directions other than that (slanting directions, and directions just to the right and the left) is the light ineffective in signal detection. This ineffective light becomes stray light. When the stray light is applied to the semiconductor substrate 1 and is absorbed in the semiconductor substrate 1, stray light carriers are generated.
The light emitted from the rear surface of the semiconductor laser element 2 also spreads 180 degrees both in the vertical and the horizontal directions (the larger the angle is, the smaller the light quantity is). Particularly, the light emitted rearward, that is, the light applied to the neighborhood of the monitor region 12 is used for detecting the light quantity of the semiconductor laser element 2. Light emitted in directions other than that (slanting directions, and directions just to the right and the left) becomes stray light. Some of the carriers generated by the stray light being applied to the bottom surface or the side surfaces of the concave portion 1a of the semiconductor substrate 1 are captured by the monitor region 12. However, most of the remaining carriers are absorbed in the semiconductor substrate 1 and become stray light carriers which adversely affect the light receiving portions 3 to 8.
The semiconductor laser element 2 is disposed with its front surface being close to an inclined side surface (front side surface) of the concave portion 1a, and most of the stray light emitted from the front surface impinges on the inclined side surface of the concave portion 1a. Therefore, the influence of the stray light carriers on the light receiving portions 3 to 8 is small. However, the distance between the rear surface of the semiconductor laser element 2 and the rear side surface of the concave portion 1a is comparatively large, the stray light emitted from the rear surface of the semiconductor laser element 2 is apt to be applied to the bottom surface and the side surfaces of the concave portion 1a. Since the distances between the light receiving portions 3 to 8 and the bottom and the side surfaces of the concave portion 1a are short, the stray light carriers generated in the periphery of the bottom surface and the side surfaces are apt to adversely affect the light receiving portions 3 to 8.
That is, by the stray light emitted from the rear surface of the semiconductor laser element 2 being directly or indirectly applied to the surface of the semiconductor substrate 1, particularly to the bottom or the side surfaces of the concave portion 1a and absorbed in the semiconductor substrate 1, stray light carriers are generated in the periphery of the concave portion 1a on the surface of the semiconductor substrate 1. In particular, the stray light carriers generated by the stray light emitted from the semiconductor laser element 2 toward the light receiving portions 3 to 8 and applied to the periphery of the concave portion 1a, that is, to the side surfaces of the concave portion 1a on the surface of the semiconductor substrate 1 are situated in the periphery of the light receiving portions 3 to 8. Likewise, the stray light carriers generated by the stray light applied to the bottom surface of the concave portion 1a are situated in the periphery of the light receiving portions 3 to 8. Consequently, the stray light carriers are absorbed by the light receiving portions 3 to 8, so that optical signals of levels higher than the actual signal levels are output from the light receiving portions 3 to 8.
The present invention is intended for solving the above-described conventional problem, and an object thereof is to provide an optical semiconductor device capable of more precisely outputting signals of optical recording media.
An optical semiconductor device according to a first aspect of the invention is provided with: a light source comprising a semiconductor laser element and emitting signal detecting light; a semiconductor substrate wherein the light source is mounted in a concave portion provided on a surface of the semiconductor substrate so that an optical axis of the signal detecting light from the light source is substantially parallel to the surface of the semiconductor substrate, and the signal detecting light from the light source is reflected at a side surface of the concave portion in a direction substantially perpendicular to the surface of the semiconductor substrate; at least one light receiving portion provided in an area outside the concave portion on the surface of the semiconductor substrate; and a light intercepting region provided at least in an area posterior to the light source on a bottom surface of the concave portion when a signal detecting light emitting side of the light source is a front side.
According to this structure, the stray light (not only direct light but also reflected light is included) emitted from the rear surface of the light source so as to spread over a wide area is prevented by the light intercepting region from intruding into the semiconductor substrate at least through the area posterior to the light source on the bottom surface of the concave portion, so that the generation of stray light carriers due to the intrusion of the stray light into the semiconductor substrate can be suppressed. Consequently, the stray light carriers can be prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
In the above-described structure, by forming the light intercepting region also in an area obliquely posterior to the light source on the bottom surface of the concave portion, the stray light is prevented from intruding into the semiconductor substrate through the area obliquely posterior to the light source on the bottom surface of the concave portion, so that the generation of stray light carriers due to the intrusion of the stray light into the semiconductor substrate can be further suppressed. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
Further, by forming the light intercepting region in an area surrounding the light source on all sides on the bottom surface of the concave portion, the stray light is prevented from intruding into the semiconductor substrate through the area surrounding the light source on all sides on the bottom surface of the concave portion, so that the generation of stray light carriers due to the intrusion of the stray light into the semiconductor substrate can be further suppressed. In this case, the stray light emitted from the front surface of the light source so as to spread over a wide area can be also prevented by the light intercepting region from intruding into the semiconductor substrate through an area in front of the concave portion on the bottom surface of the concave portion. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
An optical semiconductor device according to a second aspect of the invention is provided with: a light source comprising a semiconductor laser element and emitting signal detecting light; a semiconductor substrate wherein the light source is mounted in a concave portion provided on a surface of the semiconductor substrate so that an optical axis of the signal detecting light from the light source is substantially parallel to the surface of the semiconductor substrate, and the signal detecting light from the light source is reflected at a side surface of the concave portion in a direction substantially perpendicular to the surface of the semiconductor substrate; at least one light receiving portion provided in an area outside the concave portion on the surface of the semiconductor substrate; and a stray light carrier absorbing region provided at least in an area posterior to the light source on a bottom surface of the concave portion when a signal detecting light emitting side of the light source is a front side.
According to this structure, the stray light carriers generated due to the intrusion of the stray light (not only direct light but also reflected light is included) emitted from the rear surface of the light source so as to spread over a wide area into the semiconductor substrate at least through the area posterior to the light source on the bottom surface of the concave portion can be absorbed by the stray light carrier absorbing region. Consequently, the stray light carriers can be prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
In the above-described structure, by forming the stray light carrier absorbing region also in an area obliquely posterior to the light source on the bottom surface of the concave portion, the stray light carriers generated due to the intrusion of the stray light into the semiconductor substrate through the area obliquely posterior to the light source on the bottom surface of the concave portion can be absorbed by the stray light carrier absorbing region. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
Further, by forming the stray light carrier absorbing region in an area surrounding the light source on all sides on the bottom surface of the concave portion, the stray light carriers generated due to the intrusion of the stray light into the semiconductor substrate through the area surrounding the light source on all sides on, the bottom surface of the concave portion can be absorbed by the stray light carrier absorbing region. In this case, the stray light carriers generated due to the intrusion of the stray light emitted from the front surface of the light source so as to spread over a wide area into the semiconductor substrate through an area in front of the concave portion on the bottom surface of the concave portion can be also absorbed by the stray light carrier absorbing region. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
An optical semiconductor device according to a third aspect of the invention is provided with: a light source comprising a semiconductor laser element and emitting signal detecting light; a semiconductor substrate wherein the light source is mounted in a concave portion provided on a surface of the semiconductor substrate so that an optical axis of the signal detecting light from the light source is substantially parallel to the surface of the semiconductor substrate, and the signal detecting light from the light source is reflected at a side surface of the concave portion in a direction substantially perpendicular to the surface of the semiconductor substrate; at least one light receiving portion provided in an area outside the concave portion on the surface of the semiconductor substrate; a first light intercepting region provided at least in an area posterior to the light source on a bottom surface of the concave portion when a signal detecting light emitting side of the light source is a front side; and a second light intercepting region provided at least on, of side surfaces of the concave portion, a side surface between the light source and the light receiving portion.
According to this structure, the stray light (not only direct light but also reflected light is included) emitted from the rear surface of the light source so as to spread over a wide area is prevented by the first light intercepting region from intruding into the semiconductor substrate at least through the area posterior to the light source on the bottom surface of the concave portion, so that the generation of stray light carriers due to the intrusion of the stray light into the semiconductor substrate can be suppressed. Moreover, the stray light emitted from the light source is prevented by the second light intercepting region from intruding into the semiconductor substrate through, of the side surfaces of the concave portion, the side surface between the light source and the light receiving portion, so that the generation of stray light carriers due to the intrusion of the stray light into the semiconductor substrate can be suppressed. In this case, the stray light emitted from the front surface of the light source so as to spread over a wide area can be also prevented by the second light intercepting region from intruding into the semiconductor substrate through, of the side surfaces of the concave portion, the side surface between the light source and the light receiving portion. Consequently, the stray light carriers can be prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
In the above-described structure, by forming the first light intercepting region also in an area obliquely posterior to the light source on the bottom surface of the concave portion, the stray light is prevented from intruding into the semiconductor substrate through the area obliquely posterior to the light source on the bottom surface of the concave portion, so that the generation of stray light carriers due to the intrusion of the stray light into the semiconductor substrate can be further suppressed. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
Further, by forming the first light intercepting region in an area surrounding the light source on all sides on the bottom surface of the concave portion, the stray light is prevented from intruding into the semiconductor substrate through the area surrounding the light source on all sides on the bottom surface of the concave portion, so that the generation of stray light carriers due to the intrusion of the stray light into the semiconductor substrate can be further suppressed. In this case, the stray light emitted from the front surface of the light source so as to spread over a wide area can be also prevented by the first light intercepting region from intruding into the semiconductor substrate through an area in front of the concave portion on the bottom surface of the concave portion. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
An optical semiconductor device according to a fourth aspect of the invention is provided with: a light source comprising a semiconductor laser element and emitting signal detecting light; a semiconductor substrate wherein the light source is mounted in a concave portion provided on a surface of the semiconductor substrate so that an optical axis of the signal detecting light from the light source is substantially parallel to the surface of the semiconductor substrate, and the signal detecting light from the light source is reflected at a side surface of the concave portion in a direction substantially perpendicular to the surface of the semiconductor substrate; at least one light receiving portion provided in an area outside the concave portion on the surface of the semiconductor substrate; a first stray light carrier absorbing region provided at least in an area posterior to the light source on a bottom surface of the concave portion when a signal detecting light emitting side of the light source is a front side; and a second stray light carrier absorbing region provided at least in an area between the light source and the light receiving portion on the semiconductor substrate.
According to this structure, the stray light carriers generated due to the intrusion of the stray light (not only direct light but also reflected light is included) emitted from the rear surface of the light source so as to spread over a wide area into the semiconductor substrate from at least the area posterior to the light source on the bottom surface of the concave portion can be absorbed by the first stray light carrier absorbing region. Moreover, the stray light carriers generated due to the intrusion of the stray light emitted from the light source into the semiconductor substrate through, of the side surfaces of the concave portion, the side surface between the light source and the light receiving portion can be absorbed by the second stray light carrier absorbing region. In this case, the stray light carriers generated due to the intrusion of the stray light emitted from the front surface of the light source so as to spread over a wide area into the semiconductor substrate through, of the side surfaces of the concave portion, the side surface between the light source and the light receiving portion can be also absorbed by the second stray light carrier absorbing region. Consequently, the stray light carriers can be prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
In the above-described structure, by forming the first stray light carrier absorbing region also in an area obliquely posterior to the light source on the bottom surface of the concave portion, the stray light carriers generated due to the intrusion of the stray light into the semiconductor substrate through the area obliquely posterior to the light source on the bottom surface of the concave portion can be absorbed by the first stray light carrier absorbing region. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
Further, by forming the first stray light carrier absorbing region in an area surrounding the light source on all sides on the bottom surface of the concave portion, the stray light carriers generated due to the intrusion of the stray light into the semiconductor substrate through the area surrounding the light source on all sides on the bottom surface of the concave portion can be absorbed by the first stray light carrier absorbing region. In this case, the stray light carriers generated due to the intrusion of the stray light emitted from the front surface of the light source so as to spread over a wide area into the semiconductor substrate through an area in front of the concave portion on the bottom surface of the concave portion can be also absorbed by the first stray light carrier absorbing region. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
Further, by forming the second stray light carrier absorbing region also in an area posterior to the concave portion on the surface of the semiconductor substrate so as to serve also as a monitor region for detecting the quantity of the signal detecting light from the light source, the quantity of the signal detecting light from the light source can be detected by the second stray light carrier absorbing region. Consequently, it is unnecessary to provide an independent monitor region, so that the structure is simplified.
An optical semiconductor device according to a fifth aspect of the invention is provided with: a light source comprising a semiconductor laser element and emitting signal detecting light; a semiconductor substrate wherein the light source is mounted in a concave portion provided on a surface of the semiconductor substrate so that an optical axis of the signal detecting light from the light source is substantially parallel to the surface of the semiconductor substrate, and the signal detecting light from the light source is reflected at a side surface of the concave portion in a direction substantially perpendicular to the surface of the semiconductor substrate; at least one light receiving portion provided in an area outside the concave portion on the surface of the semiconductor substrate; and a monitor region provided on the surface of the semiconductor substrate for detecting a quantity of the signal detecting light from the light source and absorbing stray light.
According to this structure, the stray light carriers generated due to the intrusion of the stray light (not only direct light but also reflected light is included) emitted from the rear surface of the light source so as to spread over a wide area into the semiconductor substrate through the surface of the semiconductor substrate can be absorbed by the monitor region. Consequently, the stray light carriers can be prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
In the above-described structure, by forming the monitor region also in an area in the periphery of the concave portion on the surface of the semiconductor substrate, the stray light carriers generated due to the intrusion of the stray light into the semiconductor substrate through the surface of the semiconductor substrate can be effectively absorbed by the stray light carrier absorbing region. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
Further, by forming the monitor region in a U shape in an area in the periphery of the concave portion on the surface of the semiconductor substrate so as to surround the light source on the rear side and the left and right sides, the stray light carriers generated due to the intrusion of the stray light into the semiconductor substrate through the surface of the semiconductor substrate can be more effectively absorbed by the monitor region. In this case, the stray light carriers generated due to the intrusion of the stray light emitted from the front surface of the light source so as to spread over a wide area into the semiconductor substrate through, of the side surfaces of the concave portion, the side surface between the light source and the light receiving portion can be also absorbed by the stray light carrier absorbing region. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
An optical semiconductor device according to a sixth aspect of the invention is provided with: a light source comprising a semiconductor laser element and emitting signal detecting light; a semiconductor substrate wherein the light source is mounted in a concave portion provided on a surface of the semiconductor substrate so that an optical axis of the signal detecting light from the light source is substantially parallel to the surface of the semiconductor substrate, and the signal detecting light from the light source is reflected at a side surface of the concave portion in a direction substantially perpendicular to the surface of the semiconductor substrate; at least one light receiving portion provided in an area outside the concave portion on the surface of the semiconductor substrate; a light intercepting region provided at least in an area posterior to the light source on a bottom surface of the concave portion when a signal detecting light emitting side of the light source is a front side; and a monitor region provided on the surface of the semiconductor substrate for detecting a quantity of the signal detecting light from the light source and absorbing stray light.
According to this structure, the stray light (not only direct light but also reflected light is included) emitted from the rear surface of the light source so as to spread over a wide area is prevented by the light intercepting region from intruding into the semiconductor substrate at least through the area posterior to the light source on the bottom surface of the concave portion, so that the generation of stray light carriers due to the intrusion of the stray light into the semiconductor substrate can be suppressed. Moreover, the stray light carriers generated due to the intrusion of the stray light (not only direct light but also reflected light is included) emitted from the rear surface of the light source so as to spread over a wide area into the semiconductor substrate through the surface of the semiconductor substrate can be absorbed by the monitor region. Consequently, the stray light carriers can be prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
In the above-described structure, by forming the monitor region also in an area in the periphery of the concave portion on the surface of the semiconductor substrate, the stray light carriers generated due to the intrusion of the stray light into the semiconductor substrate through the surface of the semiconductor substrate can be absorbed by the stray light carrier absorbing region. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
Further, by forming the monitor region in a U shape in an area in the periphery of the concave portion on the surface of the semiconductor substrate so as to surround the light source on the rear side and the left and right sides, the stray light carriers generated due to the intrusion of the stray light into the semiconductor substrate through the surface of the semiconductor substrate can be absorbed by the monitor region. In this case, the stray light carriers generated due to the intrusion of the stray light emitted from the front surface of the light source so as to spread over a wide area into the semiconductor substrate through, of the side surfaces of the concave portion, the side surface between the light source and the light receiving portion can be also absorbed by the monitor region. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
Further, by forming the light intercepting region also in an area obliquely posterior to the light source on the bottom surface of the concave portion, the stray light is prevented from intruding into the semiconductor substrate through the area obliquely posterior to the light source on the bottom surface of the concave portion, so that the generation of stray light carriers due to the intrusion of the stray light into the semiconductor substrate can be further suppressed. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
Further, by forming the light intercepting region in an area surrounding the light source on all sides on the bottom surface of the concave portion, the stray light is prevented from intruding into the semiconductor substrate through the area surrounding the light source on all sides on the bottom surface of the concave portion, so that the generation of stray light carriers due to the intrusion of the stray light into the semiconductor substrate can be further suppressed. In this case, the stray light emitted from the front surface of the light source so as to spread over a wide area can be also prevented by the light intercepting region from intruding into the semiconductor substrate through an area in front of the concave portion on the bottom surface of the concave portion. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
An optical semiconductor device according to a seventh aspect of the invention is provided with: a light source comprising a semiconductor laser element and emitting signal detecting light; a semiconductor substrate wherein the light source is mounted in a concave portion provided on a surface of the semiconductor substrate so that an optical axis of the signal detecting light from the light source is substantially parallel to the surface of the semiconductor substrate, and the signal detecting light from the light source is reflected at a side surface of the concave portion in a direction substantially perpendicular to the surface of the semiconductor substrate; at least one light receiving portion provided in an area outside the concave portion on the surface of the semiconductor substrate; a stray light carrier absorbing region provided at least in an area posterior to the light source on the bottom surface of the concave portion when a signal detecting light emitting side of the light source is a front side; and a monitor region provided on the surface of the semiconductor substrate for detecting a quantity of the signal detecting light from the light source and absorbing stray light.
According to this structure, the stray light carriers generated due to the intrusion of the stray light (not only direct light but also reflected light is included) emitted from the rear surface of the light source so as to spread over a wide area into the semiconductor substrate at least through the area posterior to the light source on the bottom surface of the concave portion can be absorbed by the stray light carrier absorbing region. Moreover, the stray light carriers generated due to the intrusion of the stray light (not only direct light but also reflected light is included) emitted from the rear surface of the light source so as to spread over a wide area into the semiconductor substrate through the surface of the semiconductor substrate can be absorbed by the monitor region. Consequently, the stray light carriers can be prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
In the above-described structure, by forming the monitor region also in an area in the periphery of the concave portion on the surface of the semiconductor substrate, the stray light carriers generated due to the intrusion of the stray light into the semiconductor substrate through the surface of the semiconductor substrate can be absorbed by the monitor region. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
Further, by forming the monitor region in a U shape in an area in the periphery of the concave portion on the surface of the semiconductor substrate so as to surround the light source on the rear side and the left and right sides, the stray light carriers generated due to the intrusion of the stray light into the semiconductor substrate through the surface of the semiconductor substrate can be absorbed by the monitor region. In this case, the stray light carriers generated due to the intrusion of the stray light emitted from the front surface of the light source so as to spread over a wide area into the semiconductor substrate through, of the side surfaces of the concave portion, the side surface between the light source and the light receiving portion can be also absorbed by the monitor region. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
Further, by forming the stray light carrier absorbing region also in an area obliquely posterior to the light source on the bottom surface of the concave portion, the stray light carriers generated due to the intrusion of the stray light into the semiconductor substrate through the area obliquely posterior to the light source on the bottom surface of the concave portion can be absorbed by the stray light carrier absorbing region. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
Further, by forming the stray light carrier absorbing region in an area surrounding the light source on all sides on the bottom surface of the concave portion, the stray light carriers generated due to the intrusion of the stray light into the semiconductor substrate through the area surrounding the light source on all sides on the bottom surface of the concave portion can be absorbed by the stray light carrier absorbing region. In this case, the stray light carriers generated due to the intrusion of the stray light emitted from the front surface of the light source so as to spread over a wide area into the semiconductor substrate through an area in front of the concave portion on the bottom surface of the concave portion can be also absorbed by the stray light carrier absorbing region. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
An optical semiconductor device according to an eighth aspect of the invention is provided with: a light source comprising a semiconductor laser element and emitting signal detecting light; a semiconductor substrate wherein the light source is mounted in a concave portion provided on a surface of the semiconductor substrate so that an optical axis of the signal detecting light from the light source is substantially parallel to the surface of the semiconductor substrate, and the signal detecting light from the light source is reflected at a side surface of the concave portion in a direction substantially perpendicular to the surface of the semiconductor substrate; at least one light receiving portion provided in an area outside the concave portion on the surface of the semiconductor substrate; a light intercepting region provided at least in an area posterior to the light source on a bottom surface of the concave portion when a signal detecting light emitting side of the light source is a front side; and a stray light carrier absorbing region provided at least in an area between the light source and the light receiving portion on the semiconductor substrate.
According to this structure, the stray light (not only direct light but also reflected light is included) emitted from the rear surface of the light source so as to spread over a wide area is prevented by the light intercepting region from intruding into the semiconductor substrate at least through the area posterior to the light source on the bottom surface of the concave portion, so that the generation of stray light carriers due to the intrusion of the stray light into the semiconductor substrate can be suppressed. Moreover, the stray light carriers generated due to the intrusion of the stray light emitted from the light source into the semiconductor substrate through, of the side surfaces of the concave portion, the side surface between the light source and the light receiving portion can be absorbed by the stray light carrier absorbing region. In this case, the stray light carriers generated due to the intrusion of the stray light emitted from the front surface of the light source so as to spread over a wide area into the semiconductor substrate through, of the side surfaces of the concave portion, the side surface between the light source and the light receiving portion can be also absorbed by the stray light carrier absorbing region. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
In the above-described structure, by forming the light intercepting region also in an area obliquely posterior to the light source on the bottom surface of the concave portion, the stray light is prevented from intruding into the semiconductor substrate through the area obliquely posterior to the light source on the bottom surface of the concave portion, so that the generation of stray light carriers due to the intrusion of the stray light into the semiconductor substrate can be further suppressed. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
Further, by forming the light intercepting region in an area surrounding the light source on all sides on the bottom surface of the concave portion, the stray light is prevented from intruding into the semiconductor substrate through the area surrounding the light source on all sides on the bottom surface of the concave portion, so that the generation of stray light carriers due to the intrusion of the stray light into the semiconductor substrate can be further suppressed. In this case, the stray light emitted from the front surface of the light source so as to spread over a wide area can be also prevented by the light intercepting region from intruding into the semiconductor substrate through an area in front of the concave portion on the bottom surface of the concave portion. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
Further, by forming the stray light carrier absorbing region also in the area posterior to the concave portion on the surface of the semiconductor substrate so as to serve also as a monitor region for detecting the quantity of the signal detecting light from the light source, the quantity of the signal detecting light from the light source can be detected by the stray light carrier absorbing region. Consequently, it is unnecessary to provide an independent monitor region, so that the structure is simplified.
An optical semiconductor device according to a ninth aspect of the invention is provided with a light source comprising a semiconductor laser element and emitting signal detecting light; a semiconductor substrate wherein the light source is mounted in a concave portion provided on a surface of the semiconductor substrate so that an optical axis of the signal detecting light from the light source is substantially parallel to the surface of the semiconductor substrate, and the signal detecting light from the light source is reflected at a side surface of the concave portion in a direction substantially perpendicular to the surface of the semiconductor substrate; at least one light receiving portion provided in an area outside the concave portion on the surface of the semiconductor substrate; a stray light carrier absorbing region provided at least in an area posterior to the light source on a bottom surface of the concave portion when a signal detecting light emitting side of the light source is a front side; and a light intercepting region provided at least on, of side surfaces of the concave portion, a side surface between the light source and the light receiving portion.
According to this structure, the stray light carriers generated due to the intrusion of the stray light (not only direct light but also reflected light is included) emitted from the rear surface of the light source so as to spread over a wide area into the semiconductor substrate at least through the area posterior to the light source on the bottom surface of the concave portion can be absorbed by the stray light carrier absorbing region. Moreover, the stray light emitted from the light source is prevented by the light intercepting region from intruding into the semiconductor substrate through, of the side surfaces of the concave portion, the side surface between the light source and the light receiving portion, so that the generation of stray light carriers due to the intrusion of the stray light into the semiconductor substrate can be suppressed. In this case, the stray light emitted from the front surface of the semiconductor substrate so as to spread over a wide area can be also prevented by the light intercepting region from intruding into the semiconductor substrate through, of the side surfaces of the concave portion, the side surface between the light source and the light receiving portion. Consequently, the stray light carriers can be prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
In the above-described structure, by forming the stray light carrier absorbing region also in an area obliquely posterior to the light source on the bottom surface of the concave portion, the stray light carriers generated due to the intrusion of the stray light into the semiconductor substrate through the area obliquely posterior to the light source on the bottom surface of the concave portion can be absorbed by the stray light carrier absorbing region. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.
Further, by forming the stray light carrier absorbing region in an area surrounding the light source on all sides on the bottom surface of the concave portion, the stray light carriers generated due to the intrusion of the stray light into the semiconductor substrate through the area surrounding the light source on all sides on the bottom surface of the concave portion can be absorbed by the stray light carrier absorbing region. In this case, the stray light carriers generated due to the intrusion of the stray light emitted from the front surface of the light source so as to spread over a wide area into the semiconductor substrate through an area in front of the concave portion on the bottom surface of the concave portion can be also absorbed by the stray light carrier absorbing region. Consequently, the stray light carriers can be further prevented from being absorbed by the light receiving portion, so that signals of optical recording media can be more precisely output.